The overall goal of this project is to evaluate the role of cranial and facial sutures in craniofacial growth to get a better understanding for the treatment of craniofacial anomalies. The specific aims of the present study are to examine: (1) the involvement of the facial bones in experimentally (excess vitamin D2-) induced premature closure of sutures in rabbits; and (2) possible relationship between this phenomenon and cartilage differentiation in specific sutural areas, as a process distinct from the physiologic closure mechanism. The facial involvement will be analyzed cephalometrically, and a comparison will be made of the cellular and molecular events occurring at the suture lines between normal rabbits and those with experimentally induced premature closure. By using radioactive precursors and biochemical measurements changes in collagen synthesis and bone mineralization will be correlated to cellular activity. The study on the facial sutures is intended to go in parallel with a descriptive and experimental study on premature closure of cranial sutures where the efficacy of various treatment procedures is to be studied.